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Cholinesterase Tests

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Also known as: CHS; AChE; RBC Cholinesterase; Red Cell Cholinesterase; BChE; Plasma Cholinesterase; Pseudocholinesterase; PCHE
Formal name: Erythrocyte Acetylcholinesterase; Butyrylcholinesterase
Related tests: Dibucaine Inhibition; Liver Panel

Were you looking instead for acetylcholinesterase testing of amniotic fluid for neural tube defects?

At a Glance

Why Get Tested?

  • To determine if you have been exposed to and/or poisoned by certain organophosphate chemicals found in pesticides; to monitor cholinesterase levels if you work with pesticides
  • Sometimes to identify individuals with inherited pseudocholinesterase deficiency before they are given anesthesia with the muscle relaxant succinylcholine or to help determine the cause of prolonged apnea after surgical anesthesia

When to Get Tested?

  • When you have symptoms of pesticide poisoning or on a regular basis when you are at risk of exposure to organophosphates, such as through work in the agriculture industry and/or frequent use of organophosphate insecticides
  • When you or a close relative have experienced prolonged apnea and muscle paralysis after use of the drug succinylcholine for a surgical operation

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?


The Test Sample

What is being tested?

Cholinesterases are enzymes that are involved in helping the nervous system to function properly. There are two separate cholinesterase enzymes in the body: (1) acetylcholinesterase, found in red blood cells as well as in the lungs, spleen, nerve endings, and the gray matter of the brain, and (2) pseudocholinesterase (butyrylcholinesterase), found in the serum as well as the liver, muscle, pancreas, heart, and white matter of the brain. Cholinesterase tests measure the activity of these enzymes.

Acetylcholinesterase is involved in transmission of nerve impulses by breaking down acetylcholine, a chemical that helps to transmit signals across nerve endings. A decrease in the activity of the enzyme acetylcholinesterase results in excess acetylcholine at nerve endings. This can lead to overstimulation of nerves within body tissues and organs. Pseudochlinesterase is involved in processing and metabolizing drugs.

The two most common reasons for testing activity levels in the blood are:

  • Organophosphate pesticide exposure. Insecticides containing organophosphates can inhibit cholinesterase and pseudocholinesterase activity. Symptoms can be severe with acute exposure to these pesticides or can gradually appear with chronic exposure. Absorption can occur by inhalation, ingestion, or contact with the skin. Testing red blood cell acetylcholinesterase and serum pseudocholinesterase may be done to detect acute poisoning or to monitor those with occupational exposure to these chemicals, such a farm workers or those who work with industrial chemicals.
  • Inherited pseudocholinesterase deficiency. Some individuals have an inherited deficiency due to a genetic variant of the enzyme pseudocholinesterase. This enzyme is used by the body to inactivate (metabolize) succinylcholine, a muscle relaxant that is commonly used during surgery. People who have low levels or defective pseudocholinesterase may experience prolonged effects of the drug, with protracted muscle paralysis and apnea following anesthesia. In addition, those who are homozygous for genetic variants may be at greater risk of adverse effects than those who are heterozygous. Pseudocholinesterase testing can be performed prior to surgery on those with a family history of prolonged apnea after use of succinylcholine to determine if they are at risk of complications related to this drug.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

Common Questions

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Article Sources

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Sources Used in Current Review

MedlinePlus Medical Encyclopedia. Cholinesterase - blood. Available online at Accessed October 2013.

WebMD. Cholinesterase Inhibitors for Alzheimer's Disease. Available online at through Accessed October 2013.

Mayo Clinic. PCHES - Clinical: Pseudocholinesterase, Total, Serum. Available online at through Accessed October 2013.

Ralph Magnotti, PhD, DABCC. Lab Tests Online adjunct board member.

Sources Used in Previous Reviews

Ralph Magnotti, PhD, DABCC. Lab Tests Online adjunct board member.

Magnotti RA, Dowling K, Eberly JP, McConnell RS (1988). A detailed case of two severely intoxicated patients monitored for AChE, from initial insult through recovery. Described in: Field measurement of plasma and erythrocyte cholinesterases. Clin Chim Acta 176:315-332.

Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, 4th Edition: Saunders Elsevier, St. Louis, MO. Pp 250-251.

Mosby's Manual of Diagnostic and Laboratory Tests. Pagana 4th edition, Pp. 171-172.

Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Burtis CA, Ashwood ER, Bruns DE, eds. St. Louis: Elsevier Saunders; 2006, Pp 614-616.

Mayo Clinic. Unit Code 8767: Pseudocholinesterase, Dibucaine Inhibition, Serum. Available online at through Accessed November 2010.

Mayo Clinic. Acetylcholinesterase, Erythrocytes. Available online at through Accessed November 2010.

MedlinePlus Medical Encyclopedia. Serum cholinesterase. Available online at Accessed November 2010.

Environmental Protection Agency. Recognition and Management of Pesticide Poisonings, Organophosphate Insecticides. PDF available for download at through Accessed November 2010.

(September, 2009) Merck Manual. Succinylcholine Drug Information. Available online at through Accessed November 2010.

Arup Laboratories. Pseudocholinesterase, Dibucaine Inihibition. Available online at through Accessed November 2010.

(Updated May 1, 2009) Alexander D. Pseudocholinesterase Deficiency. Medscape. Available online at through Accessed November 2010.